//
// Created by jsjxsy on 2022/6/28.
//
#include<stdio.h>
int main() {
  puts("sum of n,please input n:");
  int number;
  scanf("%d", &number);
  int sum = 0;
  for (int i = 1; i <= number; i++) {
    sum = sum + i;
  }
  printf("sum of %d: %d", number, sum);
  return 0;
}